One cannot expect measurements alone to supply all of the neutron-induced activation cross-section data required by the fission reactor, fusion reactor, and nuclear weapons development communities, given the wide ranges of incident neutron energies, the great variety of possible reaction types leading to activation, and targets both stable and unstable. Therefore, the evaluator must look to nuclear model calculations and systematics to aid in fulfilling these cross-section data needs. This review presents some of the recent developments and improvements in the prediction of neutron activation cross sections, with specific emphasis on the use of empirical and semiempirical methods. Since such systematics require much less nuclear informaion as input and much less computational time than do the multistep Hauser-Feshbach codes, they can often provide certain cross-section data at a sufficient level of accuracy within a minimum amount of time. The cross-section information that these systematics can and cannot provide and those cases in which they can be used most reliably are discussed.

Neutron Cross Sections, Volume 2: Neutron Cross Section Curves presents data for total reaction cross sections and related fission parameters as a function of incident-neutron energy. This book covers energy range from 0.01 eV to 200 MeV to exclude crystalline and magnetic effects for slow neutrons and relativistic effects for high energy neutrons. The data in this volume are grouped into sections corresponding to the element of the target nucleus in the neutron-induced reaction. These sections are ordered in increasing atomic number. Within a section, graphical data are presented for the natural element followed by the isotopes of that element in order of increasing atomic mass. A list of the reaction types is provided at the end of each section. This book also provides graphical section, wherein each graphical page is annotated on the outer edge with a symbol for an element or isotope followed by the list of the cross section data for that element or isotope. The data plotted in the graphical section are tagged by a mnemonic consisting of year, laboratory, and author's last name. This tag can be used to find the corresponding reference on the bibliographic pages.

Nuclear model codes were used to calculate cross sections for neutron-induced reactions on 19F for incident energies from 2 to 20 MeV. The model parameters in the codes were adjusted to best reproduce experimental data and are given in this report. The calculated results are compared to measured data and the evaluated values of ENDF/B-V. The covariance matrix for several of the most sensitive model parameters is given based on the scatter of measured data around the theoretical curves and the long-range correlation error of measured data. The results of these calculations form the basis for the new ENDF/B-VI fluorine evaluation. 44 refs., 64 figs., 14 tabs.